2.2 Alkaline solution (sodium silicate solution from RHA)
An alternative sodium silicate solution from RHA was prepared, based on previous studies from literature (Bouzón et al. 2014; Mejía et al., 2016; Mellado et al., 2014; Tchakouté et al. 2016a, 2016b).
RHA was added to a NaOH solution and mixed with a magnetic stirrer with heating (90 °C ± 5 °C) for 30 min aiming to enhance the silica dissolution.
The total amount of soluble silica was determined by the gravimetric analysis as follows. Two solutions containing RHA, NaOH and water were produced: 1) untreated solution, which did not pass to the silica dissolution process; and 2) treated solution, which was kept for 30 min in heating and mixing. Portions of treated and untreated solutions …show more content…
2.3 Geopolymer binder
Geopolymer binder was made by the mixture of the alkaline solution with MK+WTS. A reference mixture was made without WTS.
The materials were mixed by stirring to obtain a homogeneous slurry (1 min). The molar ratios of the geopolymer matrix components used in the experiment were: SiO2/Al2O3 = 4.2; Al2O3/Na2O = 1.1; Na2O/SiO2 = 0.2; and H2O/Na2O = 13.6.
The FRX results showed WTS with lower silicon content when compared to MK. Due to this difference, RHA was added in the mixtures with WTS to supply this lack of SiO2. The proportions of the additional RHA were adjusted to have the same molar ratios in all …show more content…
The results were expressed in min, and the time was counted from the mixture of MK+WTS with the alkaline solution.
Temperature kinetics curves of the geopolymer binders were obtained with a semi-adiabatic calorimeter, which was isolated from the external environment. The test was made to observe the temperature rise with time and to verify the exothermic geopolymerization reactions in the first hours after mixing. Thermocouples (K-type) registered the temperature. Data were recorded each 10 seconds for a period of 25 h by a datalogger Testo 177-T4.
The flow (consistency) of geopolymer mortars was obtained with the flow table. The result is the mean value measured in three diameters in different directions after mortars spreading (ABNT, 2005a).
2.5.2 Flexural and compressive strengths
Flexural and compressive strength tests on mortars were performed at the ages of 1, 7, 28 and 90 days. The specimens were tested in a Versa Tester machine (maximum load of 150 kN). Flexural strength was obtained by the three-point-bending test, and compressive strength was determined on the far edge of both residual pieces obtained from flexural strength test (ABNT,
An alternative sodium silicate solution from RHA was prepared, based on previous studies from literature (Bouzón et al. 2014; Mejía et al., 2016; Mellado et al., 2014; Tchakouté et al. 2016a, 2016b).
RHA was added to a NaOH solution and mixed with a magnetic stirrer with heating (90 °C ± 5 °C) for 30 min aiming to enhance the silica dissolution.
The total amount of soluble silica was determined by the gravimetric analysis as follows. Two solutions containing RHA, NaOH and water were produced: 1) untreated solution, which did not pass to the silica dissolution process; and 2) treated solution, which was kept for 30 min in heating and mixing. Portions of treated and untreated solutions …show more content…
2.3 Geopolymer binder
Geopolymer binder was made by the mixture of the alkaline solution with MK+WTS. A reference mixture was made without WTS.
The materials were mixed by stirring to obtain a homogeneous slurry (1 min). The molar ratios of the geopolymer matrix components used in the experiment were: SiO2/Al2O3 = 4.2; Al2O3/Na2O = 1.1; Na2O/SiO2 = 0.2; and H2O/Na2O = 13.6.
The FRX results showed WTS with lower silicon content when compared to MK. Due to this difference, RHA was added in the mixtures with WTS to supply this lack of SiO2. The proportions of the additional RHA were adjusted to have the same molar ratios in all …show more content…
The results were expressed in min, and the time was counted from the mixture of MK+WTS with the alkaline solution.
Temperature kinetics curves of the geopolymer binders were obtained with a semi-adiabatic calorimeter, which was isolated from the external environment. The test was made to observe the temperature rise with time and to verify the exothermic geopolymerization reactions in the first hours after mixing. Thermocouples (K-type) registered the temperature. Data were recorded each 10 seconds for a period of 25 h by a datalogger Testo 177-T4.
The flow (consistency) of geopolymer mortars was obtained with the flow table. The result is the mean value measured in three diameters in different directions after mortars spreading (ABNT, 2005a).
2.5.2 Flexural and compressive strengths
Flexural and compressive strength tests on mortars were performed at the ages of 1, 7, 28 and 90 days. The specimens were tested in a Versa Tester machine (maximum load of 150 kN). Flexural strength was obtained by the three-point-bending test, and compressive strength was determined on the far edge of both residual pieces obtained from flexural strength test (ABNT,